What happened
During the descent phase for landing, the flight encountered an uncommanded roll to the right. At the time this event occurred, the 'B' autopilot system was engaged. The sudden movement required immediate attention from the crew as they managed the aircraft's attitude and trajectory.
The investigation
Following the incident, a thorough examination of the aircraft systems was conducted. Post-incident analysis revealed that the 'B' autopilot aileron actuator exhibited low electrical resistance. This finding prompted further testing by Boeing Commercial Airplane Company to understand the implications of this anomaly.
Findings
Tests conducted by Boeing Commercial Airplane Company demonstrated that low electrical resistance within the autopilot aileron actuator is directly linked to uncommanded roll occurrences. This mechanical issue likely contributed to the unexpected aircraft movement during the critical descent phase.